1. Field of the Invention
Orbital abrading or polishing tools have been available for many years. Examples of such tools are presented in U.S. Pat. No. 4,592,170 to Hutchins, U.S. Pat. No. 4,660,329 to Hutchins, U.S. Pat. No. 4,671,019 to Hutchins, U.S. Pat. No. 4,839,995 to Hutchins, U.S. Pat. No. 4,986,036 to Hutchins, U.S. Pat. No. 5,445,558 to Hutchins, and U.S. Pat. No. 5,597,348 to Hutchins, all of which are incorporated by reference in their entirety into the present disclosure.
2. Description of the Related Art
Orbital sanders of the prior art have, in some instances, been shaped to be held by a user in manipulating the sander and moving it along a horizontal work surface to sand that surface. Such sanders often utilize a head which carries a sheet of sandpaper and is driven rotationally by a compressed air powered motor. The motor is usually contained within a rather heavy body structure.
Typically, the head is mounted to a spindle which in turn is mounted eccentrically relative to the vertical axis of the motor so that the head orbits about the vertical axis. It is often desirable to be able quickly and easily remove the head from the drive portion of the sander in order to enable selective use of any of several heads of different sizes and shapes with a single drive unit. A drive unit and a set of different heads can then serve, in effect, as a number of different tools. In the prior art, replacing the head has been relatively difficult because tools have typically been required for unscrewing the head from the drive portion of a sander.
Previously developed portable orbital sanders have utilized a flexible shroud to provide access for insertion of a tool between the head, which is also commonly referred to as a shoe, and the housing to lock the spindle so that the head can be unscrewed manually from it. Located within the shroud and just above the spindle is a rotating counterweight used to counterbalance the eccentrically mounted spindle and head. This arrangement has several disadvantages, however. First, the flexible shroud can be pressed inwardly by an operator""s fingers until it contacts the rotating counterweight. This causes wear to the sander in addition to unwanted vibrations. Also, debris can enter the space between -the shroud and the head, and thus clog the inner workings of the sander, if the flexible shroud becomes distorted. Further, there is a risk that the fingers of the operator might enter the space, causing injury to the user.
Prior art sanders have used air control valves having rotatable cylindrical valve elements for regulating the supply of compressed air to the motor. However, in order to prevent the air pressure from ejecting the air control valve axially from the body structure, the air control valve has been secured in place within the body structure using such imprecise and makeshift methods as using a strap to hold the air control valve against the body structure.
After powering the motor, the compressed air must, of course, leave the sander. The escaping high pressure air creates a loud noise which can be harmful to the operator as well as those in the area. The noise level can be lowered by packing the output path with cotton or other materials, but this leads to the disadvantage of significantly greater back-pressure.
Prior orbital sanders have sometimes utilized a top cover secured to the body structure by screws passing downwardly through the cover and into threaded bores formed in the body structure. This method of securing the cover is disadvantageous and expensive, however, because it requires time-consuming drilling and threading of the body structure.
The orbital sander of the present invention eliminates many of the disadvantages of the prior art sanders by providing a compact, lightweight, and economical sander having a body and shroud formed from an injection-molded synthetic polymeric material. The head is replaced using a built-in plunger which engages notches in the spindle, without the need for tools. The built-in plunger enables the flexible shroud of the prior art to be replaced with a rigid polymeric shroud positioned with a minimal gap between the shroud and the head or shoe. The polymeric shroud is attached to the rest of the polymeric body structure by three screws and two pins. The pins project upwardly from the polymeric shroud and into precise engagement with the polymeric body structure, thus reducing the required drilling and tapping, providing rotational stability, and increasing the strength of the connection between the two parts. The air control valve is securely held in the housing using a set screw having a dog which engages a groove in the air control valve to resist the axial force tending to eject the air control valve from the body structure. Finally, a new muffler is used which creates a circuitous path for the exiting air, and thus dampens its acoustic energy.
To realize the advantages outlined above, one embodiment of the portable orbital abrading or polishing tool of the present invention includes: a tool body to be held and manipulated by a user; a motor carded by the body; an orbital drive structure driven rotatably about a first axis by the motor; a spindle having at least one notch along its outer circumference and which is connected to the orbital drive structure for rotation relative thereto about a second axis offset from the first axis to drive the spindle in an orbital path about the first axis as the orbital drive structure turns; a head threadedly connected to the spindle and adapted to carry an element for abrading or polishing a work surface; and a plunger passing through the body and movable radially inwardly, the plunger movable between a first position and a second position, wherein in the first position the plunger does not contact the outer circumference of the spindle and in the second position the plunger engages the at least one notch for any position of the spindle along the orbital path.